The present invention relates to fluorescent-lamp socket. More particularly this invention concerns such a socket for an instant-start fluorescent lamp.
A preheat-type fluorescent lamp has two conductor pins extending from each end between which are connected resistance-wire heater coils serving to heat electrodes each connected to one of the respective pins to initiate fluorescence the hearers in the bulb are heated briefly and then an arc is drawn between the two electrodes, whereupon the voltage differential across the pins at each end is eliminated to deenergize the heater coils. Thus the lamp is fitted at each end into a socket which allows individual connections to be made to the two pins. This is the standard system for starter-type and rapid-start fluorescent lighting fixtures.
Normally as described in German patent 195 11 887 each socket comprises a hollow dielectric housing and a pair of generally identical conductive contact elements in the housing each having an outer end adapted to engage a respective pin of the lamp, an inner end formed with a wire-engaging clip, and a center part extending between the respective inner and outer ends. Wires are shoved into holes in the housing so that their ends can be fitted to the clips to make the necessary connections.
In the newer instant-start systems no starter is employed. Instead, fluorescence is initiated by applying a very high startup voltage between the ends of the lamp. Once the lamp starts to fluoresce, the voltage is dropped to the standard running voltage. Such lamps are normally made physically the same as standard starter-type lamps so that users familiar with installing the old preheat lamps have no problems. The sockets, however have to be wired differently. More particularly for an instant-start lamp both contact elements of each socket are wired together, that is there is no voltage difference across them at any time and in fact the same voltage must be applied to both of them.
In order to reduce manufacturing costs the sockets are built basically the same for both types of lamps. A simple shunt wire is installed between the clips of the two contact elements for an instant-start lamp, but is left out for the preheat-type lamps. Since each contact element is normally formed with two such clips, this still leaves two clips free for wiring of the socket. The disadvantage of this system is that installing this extra bridge wire entails an extra production step and therefore elevates cost. Furthermore if it is not installed perfectly, the socket is defective and this defect will not be discovered until the end user tries to use the fixture incorporating it.
Accordingly it has been suggested to mount a separate bridge element in the housing of the socket so that, when the two contact elements are installed they will engage it and it will electrically interconnect them. Once again, this extra structure and the extra manufacturing step installing it increases the cost of this mass-production item excessively.
It is therefore an object of the present invention to provide an improved socket for an instant-start fluorescent lamp.
Another object is the provision of such an improved socket for an instant-start fluorescent lamp which overcomes the above-given disadvantages, that is which is of very simple construction and that is no more expensive or difficult to make than a socket for a preheat-type lamp.
A further object is to provide a conductor element for a fluorescent-lamp socket that can readily be adapted for use with preheat or instant-start lamps.
A fluorescent-lamp socket has according to the invention a hollow dielectric housing, and a pair of identical conductive contact elements in the housing, each contact element is unitarily formed with an outer lamp-contacting end adapted to engage a respective pin of the lamp, an inner wiring end formed as a, wire-engaging clip, a center part extending between the respective inner and outer ends, and an elastic tongue unitarily formed with the respective center part and projecting transversely toward the other contact element.
According to the invention the contact elements are formed of resilient sheet metal. The housing can include a web projecting between and holding apart the elastic tongues. Alternately it can be constructed such that either the tongues bear on each other and electrically interconnect the contact elements or each tongue bears on the center part of the other contact element to electrically interconnect the contact elements.
Thus with the system of this invention it is possible to use exactly the same conductor elements to make sockets both for preheat-type and instant-start fluorescent lamps. Only one of two parts of a cheap molded housing needs be changed in order for the socket to accommodate the other type of lamp. As a result manufacture costs can be held quite low.